I had a look at the instructions but I need some hand holding as they don't appear all that clear...
There are three different (power) LED blinking speeds during boot for most of the routers:
A power-on sequence of lights that is specific to the device's boot loader
Then a fast 5-per-second blinking rhythm during two seconds, while router waits for user to trigger the failsafe mode, typically by a button press
Then eitherter
A faster, 10-per-second blink if the user pressed a button and failsafe mode was triggered
A slower, 2.5-per-second blink continuing to the end of boot, if the failsafe was not triggered and the normal boot continues
The button press seems a bit ambiguous. Doesn't pressing the power button after switching it on, switch it off? Which button does it mean? Apart from the power button, there is the WPS/Reset button. Is that what it means?
Am I supposed to wait for the 5 ps blink to start and then I have two seconds in which to press the reset button to invoke the 10 ps blink?
If I'm lucky enough to enter failsafe mode should I expect my attached PC to acquire an IP address? How long should I give it? And does it matter which port on the router it is connected to?
Wait for the "gear" light on the front (next to the power light) to flash rapidly, then press and release the reset button repeatedly. If it went to failsafe mode the gear light will be flashing very rapidly.
It will stay in failsafe mode indefinitely so you can then hook up your Ethernet cable to one of the LAN ports, get a DHCP address, and SSH in to 192.168.1.1 as if it were a new install.